Graft copolymers prepared from unsaturated polyvinyl chloride and acrylic esters and method of making same



United States Patent GRAFT COPOLYMERS PREPARED FROM UNSAT- URATEDPOLYVINYL CHLORIDE AND ACRYL- IC ESTERS AND METHOD OF MAKING SAMERichard W. 'Rees, Shawinigan Falls, Quebec, Canada,

assignor to Shawinigan Chemicals Limited, Montreal,

Quebec, Canada, a corporation of Canada No Drawing. Application January22, 1957 Serial No. 635,121 4 Claims. (Cl. 260-455) This inventionrelates to unsaturated polyvinyl chloride resins and particularly to theunsaturated resins prepared by reacting polyvinyl chloride resins withammonia, and to the derivatives of said unsaturated resins.

Polyvinyl chloride in dilute solution has been treated with zinc byMarvel, Sample and Roy (J. Am, Chem. Soc., '61, 3241 (1939)). Theresulting dehalogenation with Zinc removed up to 87% of the chlorinecontent from the polyvinyl chloride and it was indicated thatcyclopropane units were formed. Marvel and coworkers found thatpotassium hydroxide removed the elements of hydrogen chloride whenheated with polyvinyl chloride in solution, and that an insolublereddish-brown polymer was formed, which they believed to be a long chainpolyene. The degradation of polyvinyl chloride films by the bases benzyltrimethyl-ammonium hydroxide and trimethyl-e-hydroxyethyl ammoniumhydroxide was examined spectrophotometrically by Campbell and Rauscher(J. Polymer. Sci., 18, 461 (1955)), who found evidenceof the formationof long conjugated polyene chains.

It has now been found that the elements of hydrogen chloride can beeliminated in part from polyvinyl chloride resins dissolved in suitablesolvents, by treatment with ammonia preferably at elevated pressure andtemperatures above room temperature, to form useful un saturatedreactive products. Too prolonged contact of vinyl chloride homopolymerresin with ammonia at elevatedtemperatnres and pressures is found toproduce polyvinyl amine to a large extent.

The invention thus comprises a process for the preparation of anunsaturated polymer from a saturated polymer selected from the groupconsisting of polyvinyl chloride and copolymers of vinyl chloride andvinyl acetate wherein the'vinyl acetate does not exceed 20% by weight ofthe total copolymer, comprising reacting a solution of the saturatedpolymer in inert solvent with ammonia at an elevated temperature andpressure whereby the elements of hydrogen chloride are removed from thepolyme: and an unsaturated polymer is produced, and recovering theunsaturated polymer from the solution, The invention also comprises thepolyvinyl chloride resins ;Which have been rendered partly unsaturatedby treatment with ammonia. The invention further comprises thederivatives of polyvinyl chloride resins, prepared by reacting partlyunsaturated polyvinyl chloride resins with substances which add todouble bonds.

When a vinyl chloride-vinyl acetate copolymer is treated with ammonia togive an unsaturated resin according to this invention, it appears fromthe infrared absorption curve of the. product that only hydrogenchloride, and not acetic acid, is eliminated. Increasing the time,temperature, or pressure during treatment of the copolymer with ammoniaproduces increasing proportions of unsaturation in the unsaturatedcopolymer product. The same general effects are observed duringtreatment of the homopolymers of vinyl chloride with ammonia up to thepoint where polyvinyl amine commences to'be formed,

at which point the product changes from an unsaturated polyvinylchloride resin to an unsaturated copolymer comprising polyvinyl chlorideand polyvinyl amine. The

Patented Oct. 13, 1959 change is readily observable by the difference incolor of the two materials, unsaturated polyvinyl chloride beingsubstantially white and stable in air, and the material containingpolyvinyl amine being dark, usually reddishbrown in color and unstablein air. These two materials also dilfer in their solubilities.

The ammonia used in the process of this invention can be liquid ammonia,or gaseous ammonia under pressure. Pressures of 40 pounds per squareinch gauge (p.s.i.g.) and above are found to be suitable. At pressuresbelow 4-0 p.s.i.g. the time required for treatment with ammonia is solong as to be impracticable. At increasing pressures of ammonia, thereaction is more rapid and the degree of unsaturation producedincreases, subject to the limitation of the formation of polyvinyl aminewhen homopolymers of vinyl chloride are used, as indicated above.

While temperatures between 20 C. and 150 C. are operable, temperaturesin the range 50-120 C. are more convenient. Temperatures higher than C.tend to cause an undesirable darkening of the product. Temperaturesbelow 50 C. require pressures much higher than 100 p.s.i.g., or anunduly long period of treatment, to give' the same degree ofunsaturation. The higher temperatures of reaction produce more rapidreactions and higher degrees of unsaturation, as do the higherpressures.

Examples of suitable inert solvents are dioxane and dimethylformamide.Certain other solvents for polyvinyl chloride, for example,cyclohexanone, tetrahydrofurane, and nitrobenzene, are unsuitable assolvents in which to treat the resin with ammonia, because ammoniareacts with these solvents.

Recovery of the unsaturated polymer product, from the solution in whichit is formed, is most readily and simply achieved by precipitating theproduct with water. Thus the solution can be poured into a relativelylarge quantity of water, or water can be added to the solution toprecipitate the unsaturated resin. In either case, the productprecipitates as a coarse granular powder. Recovery can also be achieved,for example, by evaporating the solvent from the solution; this methodis more timeconsuming and requires care to avoid partial decompositionof the product with heat.

Reaction of the polyvinyl chloride polymer or copolymer in suitableinert solvent with ammonia at elevated temperatures and pressures givesan unsaturated resin generally similar in physical properties to thestarting material. Prolonged reaction of the homopolymer with ammonia atelevated temperatures and pressures produces a reddish-brown solid whichis at least partly polyvinyl amine. For example, treatment of vinylchloride homopolymer in dimethylformamide with ammonia at 100 C. andp.s.i.g. for three hours forms a useful unsaturated polyvinyl chlorideproduct, whereas the same treatment for 16 hours forms an undesirableamount of polyvinyl amine. This polyvinyl amine material is initiallysoluble in acetone, but becomes insoluble therein on exposure to air fora short time, presumably because of the formation of the carbonate saltof the amine. Films of the reddish-brown material freshly cast fromacetone are flexible, but soon become hard and brittle on exposure toair, apparently because of their susceptibility to attack by atmosphericcarbon dioxide.

The unsaturated resins made by this invention can be reacted withsuitable reagents which improve the properties of the resins. Thusperbenzoic acid and peracetic acid can be reacted with the unsaturatedresins to intro duce epoxy groups. These groups improve solubility,filming properties, and adhesive properties of the original resins.Peracetic acid is preferred as epoxidizing agent resins 3. when suchunsaturated copolymers are reacted with perbenzoic acid.

Further, the unsaturated linkages of the unsaturated can behydrogenated, thereby introducing CH CH groups into the polymer. Thesofteningpoint is thus increased without affecting the solubility of theresins, and film flexibility is also improved.

Other monomers can be made to add to the unsaturated portions of theresins, giving graft-copolymers. Thus methyl acrylate can be graftedonto unsaturated polyvinyl chloride resin, to improve film adhesionwithout affecting the mechanical film strength and rigidity.

Numerous other uses of these unsaturated resins will suggest themselvesto those skilled in the art. The following examples illustrate, but donot limit, the scope of the invention as hereinafter claimed.

EXAMPLE 1 Fifty grams of Vinylite resin VYHH (a copolymer of vinylchloride and vinyl acetate, nominally consisting of 87 parts vinylchloride and 13 parts by weight vinyl acetate and supplied by Carbideand Carbon Chemicals Co.) was dissolved in 500 ml. dioxane. The resinsolution was placed in a 2-liter stainless steel stirred autoclave. Theautoclave was closed, the air was swept out with nitrogen, and thenitrogen was evacuated. The autoclave was then connected to a cylindercontaining gaseous ammonia under pressure. The pressure exerted by theammonia alone was 350 pounds per square inch gauge (p.s.i.g.) at 100 C.The weight of ammonia added (Table I) was obtained from loss of weightof the cylinder. The pressure was then increased to 1000 p.s.i.g. bynitrogen pressure. The autoclave was main tained at 110 C. by heatingcoils. After the mixture was heated for 6 hours, the resin product wasisolated from the solution by precipitation with water and was found tobe generally similar in solubility and film properties to the startingmaterial. This example was repeated, and chlorine and nitrogen analyseswere carried out on the product. The average nitrogen content of theproduct was 0.091%, corresponding to 0.28% vinyl amine, while averagechlorine was 44.6%, a decrease of 6.8% from the original value of 51.4%.The slight lowering of viscosity of a 0.2% solution of the product incyclohexanone (Table I) indicated that a slight degradation of theoriginal copolymer had occurred.

The product was analyzed for unsaturation by reaction with perbenzoicacid. A solution of perbenzoic acid in chloroform (57 grams per litre)was prepared by the method given in Organic Syntheses, Collective Vol.1, page 431. An excess of the solution was added to a solution of theunsaturated resin in chloroform and allowed to stand for two days at C.A blank experiment was run in parallel. Determination of the amount ofunreacted perbenzoic acid indicated that 0.204 gram perbenzoic acid hadreacted with 1.000 gram of unsaturated resin. If the value of 6.4 molepercent vinyl acetate in VYHH given by the chlorine analysis is assumed,calculation indicates the presence of 10.25 mole percent double bonds,or one double bond for every 9.8 monomer units in the product. Theexistence of unsaturation as indicated by reaction with perbenzoic acidwas confirmed by the ultraviolet absorption spectrum of the product.Infrared analysis of the product after treatment with perbenzoic acidindicated that it had much higher absorption than the starting materialin the general region characteristic for epoxy groups. A definite bandwhich has been assigned to epoxy groups was found at 868 cmf EXAMPLES 2,3 AND 4 The reactor used in Examples 2, 3, and 4 was an unstirredpressure vessel, comprising a glass tube and a steel cylinder into whichthe glass tube could be fitted snugly. The glass tube was about 18inches long and one inch in diameter, closed at the bottom and with aliquid capacity of 800 ml. The steel cylinder was closed at the bottomand flanged at the top. A flanged cover with pressure gauge attachedcould be bolted to the cylinder to maintain the contents under pressure.A weighed quantity of resin was dissolved in a solvent as indicated inTable I and cooled to -10 C. Liquid ammonia, 20 grams, was poured intothe glass tube, which had previously been cooled in Dry Ice to about -40C. The colorless resin solution was then slowly added to the glass tube.The glass tube was placed inside the steel cylinder, also previouslycooled, and the flanged cover was bolted tightly in place. The reactorwas then heated on a steam bath for either 3 or 16 hours, as recorded inTable I. The reactor was then cooled to 40 C., and the top removed. Thecontents of the glass tube were placed in a beaker to allow the ammoniato evap orate. The resin QYSJ used in Example 3 is a polyvinyl chlorideresin containing no copolymerized material, and is sold commercially byCarbide and Carbon Chemicals Co.

The results of analyses of the products for chlorine content, and formole percent unsaturation by the per benzoic acid method as described inExample 1, are listed in Table I. The amount of unsaturation in theproducts of Examples 24 was much less than that of the product ofExample I. Estimations of the proportion of unsaturation based on theareas enclosed by the ultraviolet ab sorption curves of the productswere in good agreement with the proportion of unsaturation as measuredby the perbenzoic acid method. The unsatunation as calculated from thedecrease in chlorine content, assuming one double bond for each chlorineatom lost, was more than twice as high as the value derived from theperbenzoic acid method. While the invention in no way depends on theinterpretation of this difference, it may be suggested that thedifference is due to bridge bonding, giving rise to some three-memberedrings (cyclopropane units) or is due to steric hindrance aifecting thereaction of the perbenzoic acid with the double bonds. The lowering ofthe viscosity of a 0.2% solution in cyclohexanone of the unsaturatedproduct of Example 4 indicated a slight degradation.

Table I Example No 1 2 3 4 Resin Type VYHH VYHH QYSJ VYHH. PercentChlorine in Resin 51.4%. Weight in Grams 7. Solvent Dioxaue... Di0xaueDimethyl Dimethyl Formamide Formamide.

Solvent Volume, ml 500 100. Ammonia, Weight in Grams (gas) 20 (liquid).Time, Hours. 6... 16. Temperature 0..." Pressure, p.s.i.g 1,000 ResinProduct, Color Whlte Unsaturation, Mole Percent (Perbenzoic Method)l0.25% Percent Chlorine in Product 44.6%"..- Viscosity of 0.2% Solutionin Cy ohexanone, 20 0., in centipoises:

(A) Product 2.58 (B) Original Resin... 2.64

aces-pea EXAMPLE 5 Seven grams of polyvinyl chloride resin QYSJ wasdissolved in 120 grams of dimethylformamide and 15 grams. of liquidammonia Was added, using the apparatus of Examples 2-4. Part of theammonia pressure was then released, so that the pressure in the reactorwas 42 'p.s.i.g., when heated at 100 C. Heating was continued for 16hours, after which the unsaturation of the resin was" found to be 1.6mole percent, measured by' the perbenzoic method. The unsaturatedproduct was a white resin similar in appearance to the startingmaterial.

, EXAMPLE, 6

Seven grams of resin QYSI was dissolved in 120 ml. dimethylformamide andtreated with 20 grams of liquid ammonia at 100 C. and 140p.s.i.g. in theapparatus described in Examples 2-4. The quantities of materials werethe same as in Example 3. However, the reaction was continued for 16*hours, in contrast with the 3 hours described in Example 3,"and thepressure was p.s.i.g. lower than in Example 3. The initially colorlesssolution was dark red and very viscous when removed from the pressurevesselat the end of the experiment. The product was isolated by pouringthe reaction solution very slowly into cold water with vigorousstirring, whereby the product precipitated. A small quantity of theproduct dissolved in the water and was not recovered.

The product Was a reddish-brown solid, which was slightly soluble inwater, alcohol and acetic acid, readily soluble in acetone, andinsoluble in ether and benzene. A reddish flexible film was obtained bycasting from acetone solution and drying under vacuum. The film becamehard and brittle on exposure to air and could not be redissolved inacetone. Concentrated acetone solutions of the material could be dilutedwith Water, alcohol or acetic acid without any turbidity appearing, butthe addition of dilute mineral acid or alkali solutions precipitatedflocculent brown material which could be dissolved only indimethylformamide. Chlorine and nitrogen analyses were inconsistent, anddepended on the length of time of exposure of the material to air;apparently the material underwent reaction with atmospheric carbondioxide. The apparent formation of carbonates on exposure to airindicated that the product was in part polyvinyl amine.

EXAMPLE 7 This example illustrates the preparation of a graft copolymer.4.0 grams of unsaturated resin product as prepared in Example 3 wasdissolved in 35 ml. of tetrahydrofurane, and 4 grams of methyl acrylatemonomer and 0.2 gram tert-butyl hydroperoxide (70% active ingredient)were added. The mixture was stirred and then allowed to stand overnightat room temperature. The liquid was then poured slowly into 2 liters ofwater and the solid resin thus precipitated was filtered, washed 3 moretimes with water, and finally dried in a vacuum desiccator. The weightafter drying was 4.5 grams. There was no weight loss when a sample ofthe resin was immersed in methanol.

Two-mil (0.002 inch thick) films of the graft copolymer and of theoriginal QYSJ resin were prepared by casting from tetrahydrofurane. TheWeight loss of the film product in 50 ml. acetone for 16 hours was lessthan that of the original QYSJ resin, as shown in Table The adhesion offilms of the graft-copolymer to glass, Wood and metal was markedlybetter than that of unmodified QYSI resin films. Film flexibility,strength, and.

fusion temperature were found to be the same as for QY SJ resin.

EXAMPLE 8 This example describes "the hydrogenation of the unsaturatedresin. 2.00 grams of resin prepared as in Example was dissolved in 50ml. dioxane; 1 ml. of acetic acid and 0.05 gram palladium black wereadded, and the mixture was hydrogenated at atmospheric pressure; 18 ml.of hydrogen was taken up after 3 hours. The liquid was decanted from thepalladium after centrifuging and the product was isolated byprecipitation EXAMPLE 9 Example 9 illustrates the preparation of epoxyderivatives. Ten grams of VYHH resin was dissolved in ml. dioxane andtreated with 20 grams ammonia at 50 C. and 100 p.s.i.g. for 16 hours.The product was a white resin containing 2.05 mole-percent unsaturation,according to perbenzoic acid analysis.

2.00 grams of this product was dissolved in 30 ml. ethyl acetate andtreated with 2.0 ml. of 18% peracetic acid in ethyl acetate. Thesolution was heated to 50 C. for 6.5 hours and then allowed to standovernight at room temperature. The product was isolated by precipitationin 2 liters of Water. The white resin was filtered, washed thoroughlywith water and dried in a vacuum desiccator. The resin was readilysoluble in acetone and films were cast from acetone solution which hadbetter clarity, cohesion and adhesion to glass and metal than had VYHHfilms cast under the same conditions.

When a polyvinyl chloride resin is treated with ammonia, the amount ofunsaturation in the resultant product is found to depend upon the typeof resin (i.e. homopolymer or copolymer), the temperature and pressureduring treatment, the solvent, and the length of time of treatment. Theselection of pressures and other suitable reaction conditions which willgive a desired degree of unsaturation, and avoid the formation of anundesirable amount of polyvinyl amine from the homopolymer, can be madeaccording to the time and capacities of the elements of appartusavailable for the reaction.

It will readily be understood by those skilled in the art that manypolymerizable compounds in addition to methyl acrylate can form graftcopolymers with the unsaturated products of this invention. Similarly,many substances which add to double bonds can be reacted with theunsaturated'products of this invention, to form new products withimproved properties.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that the invention is not limited to the specific embodimentsthereof except as defined in the appended claims.

What is claimed is:

1. A process for the preparation of a graft copolymer derived from asaturated polymer of the group consisting of polyvinyl chloride andcopolymers of vinyl chloride and vinyl acetate wherein the vinyl acetatedoes not exceed 20% by weight of the total copolymer, comprisingreacting, under polymerizing conditions in the presence of apolymerization catalyst comprising an organic peroxygen compound, (1) alower alkyl ester of acrylic acid, and (2) an unsaturated polymerprepared by"(a) reacting a solution of said saturated. polymer, in aninert solvent of the group consisting of dioxane and dimethylformamide,with ammonia at a temperature between 20 C. and 150 C. and a pressurebetween 40 p.s.i.g. and 100 p.s.i.g. whereby hydrogen chloride isremoved from the polymer and an unsaturated polymer is produced, and (b)recovering the unsaturated polymer from the solution.

2. A product prepared by the process claimed in 8'- consisting ofdioxane and 'dimethylformamide, with ammonia at a temperature between C.and 150 C. and a pressure between 40 p.s.i.g. and pLs.i.g. wherebyhydrogen chloride is removed from the polymer and an, unsaturatedpolymer is produced and (b) recovering the unsaturated polymer from thesolution.

4. A product prepared by the process claimed in claim 3.

References Cited in the file of this patent UNITED STATES PATENTS2,304,637 Hardy Dec. 8, 1942 2,572,315 Campbell Oct. 23, 1951 FOREIGNPATENTS 618,902 Great Britain Mar. 1, 1949 OTHER REFERENCES Alfrey etal.: Journal American Chem. Soc., June 20 1951, volume 73, pages2851-2853.

1. A PROCESS FOR TE PREPARATION OF A GRAFT COPOLYMER DERIVED FROM ASATURATED POLYMER OF THE GROUP CONSISTING OF POLYVINYL CHLORIDE ANDCOPOLYMERS OF VINYL CHLORIDE AND VINYL ACETATE WHEREIN THE VINYL ACETATEDOES NOT EXCEED 20% BY WEIGHT OF THE TOTAL COPOLYMER, COMPRISINGREACTING, UNDER POLYMERIZING CONDITIONS IN THE PRESENCE OF APOLYMERIZATION CATALYST COMPRISING AN ORGANIC PEROXYGEN COMPOUND, (1) ALOWER ALKYL ESTER OF ACRYLIC ACID, AND (2) AN UNSATURATED POLYMERPREPARED BY (A) REACTING A SOLUTION OF SAID SATURATED POLYMER, IN ANINERT SOLVENT OF THE GROUP CONSISTING OF DIOXIDE AND DIMETHYLFORMAMIDE,WITH AMMONIA AT A TEMPERATURE BETWEEN 20* C. AND 150*C. AND A PRESSUREBETWEEN 40 P.S.I.G. AND 100 P.S.I.G. WHEREBY HYDROGEN CHLORIDE ISREMOVED FROM THE POLYMER AND AN UNSATURATED POLYMER IS PRODUCED, AND (B)RECOVERING THE UNSATURATED POLYMER FROM THE SOLUTION.